1. Field of the Invention:
The present invention relates to a protective beam for reinforcing automobile side doors; more particularly, it pertains to a protective beam which is adapted to be secured to an inner panel or pillar portion of the side door to provide higher mechanical strength, and thus improved safety for passengers.
2. Description of the Prior Art:
Such a protective beam is known e.g. from Japanese Patent Application Laid-open Publication No. 61-157427. The known protective beam includes an elongate main body formed of a steel sheet member of corrugated cross-section, with alternately arranged ridge and groove portions. Generally, in order to realize a sufficient mechanical strength of the protective beam, the steel sheet member is formed such that the height of a ridge portion is substantially the same as its width. The steel sheet member has longitudinal end regions each affording a shallow and generally flat mounting seat which conforms with the surface of the inner panel or pillar portion of the side door where the beam is to be stably and positively secured. In order to form the mounting seat with a desired configuration, each ridge portion of the steel sheet member along its end region is deformed to have a gradually decreased height.
The above-mentioned arrangement of the known protective beam suffers from an essential disadvantage that, due to a substantial height of the ridge portion in relation to its width, it is difficult to realize the desired configuration of the end region of the main body. Although a shallow and generally flat mounting seat may readily be formed when the ridge portion is made to have a lower profile or smaller height along the entire length thereof, this is possible only with the sacrifice of the mechanical strength whereby the protective beam cannot withstand an impact force placed on the side door e.g. upon crush or collision of the automobile.